Trulia just released some very compelling charts and graphs based off of recent opinion research suggesting it might be the end of the McMansion — the huge, mass-produced housing form associated with sprawl.

Their data, together with the drop in lot sizes for single family homes I wrote about last month, might point to a slackening in the demand for homes with lots of square footage. While this likely doesn’t mean a mass exodus of people from outer belts of sprawl into condominiums inside urban growth boundaries, it is a promising trend in tastes and economics that could be leveraged. Maybe now is the time to advance some policies to sustain this momentum. First, let’s check out the charts and graphs.

Here’s one that shows the evolution of American home preference from the 1950s to the present. House size exploded from an average of 983 square feet to more than twice that — 2,330 square feet today:

Images: Trulia

But it appears from Trulia’s research that American’s are shifting their expectations about the size of their homes. This chart shows the American’s ideal home size now:

Less than 10 percent of Americans consider the McMansion — defined by Trulia as 3,200 square feet or larger — as being the ideal home size. Not all big houses are McMansions, however. Trulia is talking here about big houses, all built at once, and sprawling out. It’s the kind of housing form you’d expect in, say, Texas. But a story on CNBC had these two shocking paragraphs:

Diane Cheatham, owner of Urban Edge Developers in Dallas, said today, the average size of home they’re building is 2,200 square feet, down from 2,500 in 2005 — which was considered small for Dallas back then.

She said the trend there is more toward building green homes instead of big homes. Right now, they’re building a 1,200-square-foot uber-green home for a couple that’s downsizing from 3,000-square feet, Cheatham explained.

And here we were thinking everything was bigger in Texas. There isn’t any clear consensus about why this is happening, though it seems certain that the economy — and unemployment in particular — has a role:

But we know density and smaller homes are better than mega houses connected by vast networks of highways. What if we made the best of this situation by creating some policies to make it more economical to live inside urban growth boundaries? One idea is what I call the Urban Homesteader Tax Exemption. If you buy a home in certain in-city areas — perhaps the Pearl District in Portland or Belltown in Seattle — you’d get a significant federal tax credit like the now expired  tax credit for first time home buyers. This would be a boon for older couples downsizing and a huge incentive for first time homebuyers. And it incentivizes what we know to be better — living in compact communities.

This post originally appeared at Sightline’s Daily Score blog.

Here is a video preview of the series now airing on PBS (it isn’t nearly as good as this classic clip from 2001: A Space Odyssey, which offers an alternative explanation of human evolution).

No, primitive humans didn’t emerge because they built windmills and held climate conferences. What proved crucial to changing the pattern of human evolution, according to the theory, was a period of extreme shifts in climate which favored species that were smarter and able to adapt more quickly to their environment. The proponent of this theory, Richard Potts director of the Smithsonian Institution’s Human Origins Program, argues that environmental instability and change was the key ingredient that propelled evolutionary change.

The [Variability Selection] hypothesis differs from prior views of hominid evolution . . .  According to the VS hypothesis, wide fluctuations over time created a growing disparity in adaptive conditions . . . Key hominid adaptations, in fact, emerged during times of heightened variability. Early bipedality, encephalized brains, and complex human sociality appear to signify a sequence of VS adaptations – i.e., a ratcheting up of versatility and responsiveness to novel environments experienced over the past 6 million years.

Sounds complicated but put simply, when the going got tough, the tough (and smart) got going. As water supplies grew and then shrank creating difficulty for early pre-human and human species, those with the ability to walk to other sources of food and water survived, while other species—more like modern day monkeys—died out. The Nova series suggests that brain development reached a plateau among pre-human and early human species at some point, but then started to take big leaps, resulting in larger more complex brains. Potts argues that those changes were spurred by huge changes in climate which favored species that were smart and agile enough to stay ahead of starvation.

There’s an energy efficiency link too, but it’s not obvious. Another scientist suggests that part of the secret of the success of our earlier ancestors was, obviously, their ability to walk. But why would that make such a big difference? Couldn’t a chimp-like ancestor have just as easily swung from tree to tree or ambled on four legs from a dried up lake to a new water source?

It all comes down to the efficient use of energy. As my colleague Clark Williams Derry has pointed out in his post on SUVs and Snickers Bars and one on bikes and energy, our concepts of energy are woefully out of sync with how energy consumption actually works. Things we assume take lots of energy often don’t, while other things we assume are not energy intensive actually are. Walking upright turns out to be a huge leap forward in the efficient use of energy.

Daniel E. Lieberman, a Harvard anthropologist featured on the Nova program has studied the relative energy used for human and chimp walking. There is no contest: human walking is far more energy efficient that the usual four legged amble of our chimp cousins.  When trying to move across many miles of African savanna to a new food source, conserving energy is crucial. Use too much of it and you’ll starve to death, but use your calories efficiently and you’ll make it to the next pile of snickers bars.

In the first installment of the series, Lieberman says that the chimp walk is “poorly designed to withstand the forces of gravity. It has to expend a lot of muscular effort to keep itself from collapsing into a little pile of chimpness, or whatever, with each step.” But walking on two legs is faster and more efficient.  Another study by Lieberman and University of Utah biologist Dennis Bramble suggests that the ability to run put even more distance between humans and our monkey cousins.

The series is provocative and fun to watch. But it also relates to issues that the human race faces today. It isn’t a stretch to wonder weather we’ve learned anything from previous effects of climate change, however ancient. Will we use our smarts to make changes in our behavior that reduce climate change? Will we work toward more efficient use of energy? Or will we be a victim of evolution like some of our less fortunate relatives? It is hard to exaggerate the long term importance of policy changes now being considered by governments all over the world. Here in North America, passing cap and trade, creating real energy efficiencies, and tapping into renewable sources of energy. This time our fate is largely in our own hands.  

This post originally appeared at Sightline’s Daily Score blog.

Blaming the food industry might be an easy thing to do. But a combination of policies that improve what we eat and encourage alternative transportation is the recipe we need to follow.

Dr. Boyd Swinburn comes down on the side of blaming the industry. A recent study he presented at the 2009 European Congress on Obesity suggests that an absence of physical activity isn’t the primary cause of the “obesity epidemic” in America – but the tactics and practices of our food industry.  

 ”The food industry has done such a great job of marketing their products, making the food so tasty that it’s almost irresistible, pricing their products just right, and placing them everywhere, that it is very hard for the average person to resist temptation. Food is virtually everywhere, probably even in churches and funeral parlors.”

Hmmm. Churches and funeral parlors? Well I can’t say I disagree with Swinburn’s point about eating too much. It is true. Eating is about energy. After all the term “calorie” is a measure of the energy embodied in food. Counting calories also give us a sense of how much exercise we have to do to ‘burn off’ that donut. The more we eat the more difficult it can be to offset our food consumption with exercise.  And some of us—myself included—live to eat while others eat to live.

As a matter of fact, we just had a discussion at Sightline’s regular staff meeting about the fact that lately a lot of baked goods have been appearing in the office. We didn’t go so far as to declare a moratorium on baking sweets and sharing them with one another, but everyone agreed that the mere presence of Eric Hess’ fantastic banana bread is enough to make us ingest some extra “energy.”

And we have been eating more. Check out this chart that shows that as Americans our calorie intake has increased by over 500 calories per day over the last 30 years. That equates to almost one extra Hostess apple pie every day.

In the most basic terms, calories are a measure of energy and it is good to reduce our caloric intake in general to the amounts we really need to maintain life and health — not extra weight. Much of the food we eat at any given meal – or snack — is loaded with enough calories, or energy, to feed a small village. And Swinburn argues that our “physical-activity levels haven’t really changed all that much.”  

But here is another fact. Our commutes are longer. According to the US Census Americans spend more than 100 hours commuting to work each year mostly in cars. And while it’s true that we are eating more calories we also have been spending a lot more time in our cars – sitting.

So it’s both. We need to start eating less and better but burning more calories is important as well. The latest information is that Vehicle Miles Traveled (VMT) in the United States and the Northwest are down and transit ridership is up. That is a positive trend no matter how you slice it. It could mean that along with reducing our impacts on climate change by sitting in our cars less, we’ll also be a lot healthier and physically active (walking to the bus). It will be interesting to see whether falling VMT will be reflected in lower obesity rates.

This post originally appeared at Sightline’s Daily Score blog.